# Copyright (c) 2007 Chris Moyer http://coredumped.org
#
# Permission is hereby granted, free of charge, to any person obtaining a
# copy of this software and associated documentation files (the
# "Software"), to deal in the Software without restriction, including
# without limitation the rights to use, copy, modify, merge, publish, dis-
# tribute, sublicense, and/or sell copies of the Software, and to permit
# persons to whom the Software is furnished to do so, subject to the fol-
# lowing conditions:
#
# The above copyright notice and this permission notice shall be included
# in all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
# OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABIL-
# ITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT
# SHALL THE AUTHOR BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, 
# WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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# IN THE SOFTWARE.

from ds import DataSource

class Derive(DataSource):
	"""
	Derive will store the derivative of the line going from the 
	last to the current value of the data source. This can be 
	useful for gauges, for example, to measure the rate of people
	entering or leaving a room. Internally, derive works exactly
	like COUNTER but without overflow checks. So if your counter
	does not reset at 32 or 64 bit you might want to use DERIVE
	and combine it with a MIN value of 0.

	Name: The name of this DS
	Heartbeat: How often we must be updated before we are "unknown" default 300 seconds
	Min: Minimum value to be stored. Default 0
	Max: Maximum value to be stored. Default None (unbounded)
	"""
	def __init__(self, name, hb=300, min=0, max=None):
		self.name = name
		self.type = "DERIVE"

		if(min is None):
			min = "U"
		if(max is None):
			max = "U"

		self.arguments=str(hb)+":"+str(min)+":"+str(max)
